| 摘要 |
PURPOSE:To effectively separate signal components and noise components and to surely monitor a transmission line by detecting a strongly modulated frequency component peculiar for strongly modulated transmitted signals from signals branched from the inside of the optical transmission line. CONSTITUTION:In the preceding step of an optical amplifier 42, the optical signals are branched by a light splitter 41 and transmitted to a transmission monitor circuit 10. The transmission monitor circuit 10 is composed of a photodetector 11 to convert input signals to electric signals, narrow band pass filter 12 to pass only the strongly modulated frequency component peculiar for the transmitted signals, and wattmeter 13 to measure the power of those output electric signals, and the measured value of the wattmeter 13 is outputted as the monitored result. Thus, since the strongly modulated frequency component peculiar for the transmitted signals is filtered by the narrow band pass filter 12, power in proportion to the power of signal light can be detected, and the optical transmission line can be monitored regardless of noise light. |
